The present invention relates to a shift register having a skip function, and a display driver device, a display device, and an electronic instrument using the same.
A conventional shift register includes N stages of transfer elements which transfer N data signals sequentially input within one cycle. N clock signals are input to the shift register within one cycle. Each of the N stages of transfer elements holds the input data signal instead of the data signal which has been held by that transfer element based on the clock signal. 1-bit data is sequentially shifted at each clock cycle in this manner.
In the case of driving a fluorescent display tube, display data and non-display data must be alternately written into the transfer elements of the shift register.
In this case, it is necessary to transfer data by alternately inputting display data and non-display data (data “0”, for example) to the shift register as the N signals while inputting N clock signals to the shift register.
As described above, since the non-display data must also be written into the shift register, the transfer time is increased. Moreover, since image processing of the non-display data is necessary, load imposed on an MPU or CPU is increased. Furthermore, it is necessary to secure the memory capacity required for the image processing of the non-display data.
Japanese Patent Application Laid-Open No. 5-19714 discloses a line-sequential drive method which can be applied to a fluorescent display tube. However, Japanese Patent Application Laid-Open No. 5-19714 discloses neither a specific example of the above-described drive of the fluorescent display tube nor its data transfer.